Montas was recalled from Triple-A Nashville ahead of his scheduled start Sunday against the Diamondbacks, Jane Lee of MLB.com reports.
Montas will step into the rotation spot of Brett Anderson (shoulder), who was replaced by long reliever Josh Lucas last week as part of a bullpen game. The 25-year-old Montas, who has worked exclusively as a starter at Triple-A this season and has produced a 4.39 ERA and 1.34 WHIP across 41 innings, offers a more conventional rotation replacement, but he'll need to perform adequately Sunday to earn additional starts. If Montas is unable to deliver quality innings for the Athletics, Kendall Graveman would likely be next in line for a promotion from Triple-A to fill Anderson's spot.